Flash spun sheet material having improved breathability

Abstract

A process is disclosed for flash spinning a nonwoven fibrous sheet from a polymeric solution containing about 12% to 33% by weight of filler particles. The filler is preferably insoluble in the polymer. The resulting plexifilamentary film-fibril sheet material has increased breathability with no decrease in liquid barrier.

1 . A nonwoven fibrous sheet comprising: 
 a) continuous lengths of plexifilamentary film-fibril strands of a polymer capable of being flash spun and    b) a filler, wherein the filler comprises 12 to 33% by weight of the plexifilamentary film-fibril strands.    
     
     
         2 . The nonwoven fibrous sheet of  claim 1 , wherein the filler comprises 12 to 33% by weight of the plexifilamentary film-fibril strands  
     
     
         3 . The nonwoven fibrous sheet of  claim 1 , wherein the filler is insoluble in the polymer.  
     
     
         4 . The sheet of  claim 1 , wherein the filler is selected form the group consisting of calcium carbonate, inorganic pigments, carbon black, clay, mica, talc, hydrotalcites, magnesium hydroxides, silica, silicates, hollow silicate spheres, wollastonite, feldspar, kaolin, glass spheres, synthetic carbonates, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, aluminum hydroxide, calcium oxide, magnesium oxide, alumina, asbestos powder, glass powder, and zeolite.  
     
     
         5 . The sheet of  claim 1 , wherein the filler is calcium carbonate.  
     
     
         6 . The sheet of either one of claims  1 - 5 , wherein the sheet has a Gurley Hill porosity of less than about 23 seconds, a basis weight of up to about 2 oz/yd 2  (67.8 g/m 2 ) and a hydrostatic head of greater than about 62 inches (157 cm).  
     
     
         7 . The sheet of either one of claims  1 - 5 , wherein the sheet has a Gurley Hill porosity of less than about 34 seconds, a basis weight of greater than about 2 oz/yd 2  (67.8 g/m 2 ) and a hydrostatic head of greater than about 84 inches (213 cm).  
     
     
         8 . A process for making a nonwoven fibrous sheet comprising flash spinning a mixture comprising a polyolefin and a spin agent, wherein the mixture further comprises a filler wherein the filler comprises 12% to 33% by weight of the nonwoven fibrous sheet.  
     
     
         9 . The process of  claim 8 , wherein the filler is insoluble in the polymer.  
     
     
         10 . The process of  claim 8 , wherein the filler is selected from the group consisting of calcium carbonate, inorganic pigments, carbon black, clay, mica, talc, hydrotalcites, magnesium hydroxides, silica, silicates, hollow silicate spheres, wollastonite, feldspar, kaolin, glass spheres, synthetic carbonates, magnesium carbonate, barium carbonate, magnesium sulfate, barium sulfate, calcium sulfate, aluminum hydroxide, calcium oxide, magnesium oxide, alumina, asbestos powder, glass powder, and zeolite.